Device and method for controlling movie camera shutter speed

Television – Camera – system and detail – Optics

Reexamination Certificate

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Details

C396S245000

Reexamination Certificate

active

06404457

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a device and a method for controlling movie camera shutter speed, more particularly to a device and a method for controlling movie camera shutter speed, which can control shutter speed appropriately in a low brightness environment by making the camera sense the environmental brightness in a manual mode.
FIG. 1
is a block diagram showing the entire system of a conventional manual shutter speed control device.
As shown in
FIG. 1
, the shutter speed control device of a conventional art includes a function key part
1
, a microcomputer
2
, a timing signal generation part
3
, a CCD(Charge coupled device)
4
, and a signal processing part
5
.
The function key part
1
selects the mode of shutter speed.
The microcomputer
2
determines a shutter speed mode in response to a signal received from the function key part
1
, and applies the signal to the timing generation part
3
.
The timing generation part
3
controls timing of CCD operation pulses in response to a signal received from the microcomputer
2
.
The CCD
4
properly charges electricity therein according to the signal received from the timing generation part
3
, and the signal processing part
5
generates video signals by processing the signals received from the CCD
4
.
When a proper key of the function key part
1
is pressed in order to put the camera into a certain shutter speed mode, the microcomputer
2
determines a shutter speed mode in response to a signal received from the key, and applies appropriate control voltage to the timing generation part
3
.
TABLE I shown below represents the relationship between the shutter speed control voltage(SSC) and the shutter speed mode.
TABLE I
MODE
SSC1
SSC2
SSC3
1/60
L
L
L
1/125
L
L
H
1/250
L
H
L
1/500
L
H
H
1/1000
H
L
L
1/2000
H
L
H
1/4000
H
H
L
1/10000
H
H
H
The control signal SSC
1
, SSC
2
and SSC
3
applied to the timing generation part
3
from the microcomputer
2
control timing signal generation so that a charging period of time of electricity in the CCD
4
can be appropriately controlled.
The timing signals from the timing generation part
3
control the CCD
4
, and the signals from the CCD
4
are applied through the signal processing part
5
.
However, the conventional shutter control device has problems in that it has to be operated in an exclusive manual mode in case it is in a manual mode, and, in case of retrieving to a normal mode, it should be retrieved into the normal mode, not by instant shifting of the mode, but by proceeding through each step of modes from the low brightness mode to the normal mode.
In other words, in case of shifting back into a normal mode from shooting an object at a shutter speed mode of {fraction (1/500)} sec. mode, it should go through the modes of {fraction (1/1000)} sec., {fraction (1/2000)} sec., {fraction (1/4000)} sec. and {fraction (1/10000)} sec. until it completely retrieves back to a normal mode, which inevitably makes viewers watch an undesired quality of pictures since pictures taken going through the above modes from a low brightness mode are made extremely dark and unrefined.
FIG. 2
is a block diagram showing entire system of a conventional automatic shutter speed controlling device.
As shown in
FIG. 2
, the conventional automatic shutter speed control device includes a lens part
6
, a hole voltage detection part
7
, a hole voltage amplification part
8
, a hole voltage offset part
9
, an ASC operation part
10
, a microcomputer
11
, a timing signal generation part
12
, a CCD
13
, a signal processing part
14
, a reference voltage generation part
15
and an ASC key part
16
.
The lens part
6
includes many lenses and the hole voltage detection part
7
connected to the lens part
6
for detecting hole voltage with sensing an extent of opening of an iris.
The hole voltage amplification part
8
amplifies weak voltage received from the hole voltage detection part
7
enough to perform ASC at the ASC operation part
10
.
The reference voltage generation part
15
generates a reference voltage for operating the hole voltage detection part
7
and the ASC operation part
10
.
The ASC operation part
10
generates a control voltage for converting the shutter speed mode in response to the signals received from the hole voltage amplification part
8
, the hole voltage offset part
9
, and the reference voltage generation part
15
.
The hole voltage offset part
9
determines an offset of the hole voltage.
The microcomputer
11
generates a control voltage for controlling shutter speed in response to the signals received from the ASC operation part
10
and the ASC key part
16
.
The timing signal generation part
12
generates timing signals in response to signals received from the microcomputer
11
.
The CCD
13
converts signals received from the timing signal generation part
12
into electrical signals and the signal processing part
14
processes signals received from the CCD
13
.
The reference voltage for operation received from the reference voltage generation part
15
is applied to the hole voltage detection part
7
and the ASC operation part
10
.
In response to the reference voltage received from the reference voltage generation part
15
, the hole voltage detection part
7
connected to the lens part
6
detects a hole voltage with an extent of opening of the iris sensed.
The hole voltage from the hole voltage detection part
7
is, amplified at the hole voltage amplification part
8
, and applied to the ASC operation part
10
.
Signals from the hole voltage amplification part
8
, the reference voltage generation part
15
and the hole voltage offset part
9
are applied to the ASC operation part
10
for generating a control voltage for controlling shifting of the shutter speed mode.
Voltage from the ASC operation part
10
is applied to the microcomputer
11
for generating a control voltage for controlling the shutter speed.
In other words, since the iris contracts when the environmental illumination becomes brighter, causing the ASC operation part
10
to output a higher voltage, a control voltage value which leads to a higher shutter speed mode is generated at the microcomputer
11
.
And, since the iris expands when the environmental illumination becomes darker, causing the ASC operation part
10
to output a lower voltage, a control voltage value which leads to a lower shutter speed mode is generated at the microcomputer
11
.
For example, the shutter speed changes from {fraction (1/125)} sec. to {fraction (1/250)} sec., or from {fraction (1/250)} sec. to {fraction (1/125)} sec, respectively.
FIG. 3
shows the hysterisis characteristic in camera iris and
FIG. 4
shows ASC changes according to brightness.
However, since the conventional automatic shutter speed control device accompanies hysterisis according to the operation voltages in opening and closing movement of the iris as shown in
FIG. 3
, and with deviation between sets, detection of an extent of iris opening from the operation voltage can not be corrected.
And, as shown in
FIG. 4
, since the ASC function can only be performed by detecting the extent of a permanent opening of the iris, it is hard to perform an accurate ASC function.
Therefore, since the conventional automatic shutter speed control device is only able of operating with two or three modes, such as {fraction (1/125)} sec., {fraction (1/250)} sec., {fraction (1/500)} sec. or {fraction (1/125)} sec., {fraction (1/250)} sec., respectively, it has problems in that the shutter speed of a movie camera can not be controlled properly and accurately according to the environmental brightness.
SUMMARY OF THE INVENTION
The object of the present invention is to eliminate the foregoing problems by providing a device and a method for controlling movie camera shutter speed, which can provide clearer images on reproduction of the recording by limiting a shutter speed mode in a low brightness with a perceived brightness at performing a manual mode.
Other object of the present invention is to provide a device a

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